Cell BiologyTopic 1

Question 1

What is osmosis

Answer 1

Osmosis is the movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water conc

Question 2

What is a partially permeable membrane

Answer 2

A membrane that allows small molecules like water to pass through it but prevent large molecules like sugar or proteins to pass through

Question 3

Osmosis practical

Answer 3

Potato experiment
Cut potato cylinders into equal slices
Measure its initial mass
Get a beaker with different sugar solutions. One should be pure water and then others with concentrated solutions from 0.2 mol/dm3 to 1mol/dm3.
Now add a potato in each cylinder for 24 hours
Remove the potato and dry them measure there masses again.
Now calculate percentage change in mass.
Dependent variable mass of potato
Independent variable conc of sugar in solution

Question 4

Factors effecting osmosis

Answer 4

Water potential gradient
Surface area
Thickness of membrane
Temperature

Question 5

What is diffusion

Answer 5

Diffusion is the spreading out of particles from an area of higher concentration to an area of lower concentration

Question 6

What is active transport

Answer 6

Movement of particles from a low to high concertation against the conc gradient

Question 7

What is the equation for magnification
What is the conversion from millimetres - micrometer - nanometers

Answer 7

Magnification =image size / real size
mm~~>um x1000 ~~> x1000

Question 8

What are the main differences between prokaryotic and eukaryotic cells?

Answer 8

Eukaryotic are complex cells and are either a plant or an animal cell
Prokaryotic are smaller and simpler and are singled celled and do not contain a nucleus

Question 9

What is the role of the nucleus in a cell?

Answer 9

The nucleus controls cell activities, stores genetic material (DNA), and coordinates cell division and protein synthesis

Question 10

What is the function of the mitochondria?

Answer 10

Where all the reactions take place in a cell and transfers energy

Question 11

How does the cell membrane control the movement of substances?

Answer 11

As the cell membrane has a partially permeable membrane, allowing certain substances to pass through by diffusion, osmosis, or active transport.

Question 12

What is the role of ribosomes in a cell?

Answer 12

protein synthesis

Question 13

What is osmosis?

Answer 13

Osmosis is the movement of water molecules through a partially permeable membrane from an area of higher water concentration (dilute solution)to an area of lower water concentration (concentrated solution).

Question 14

What is the structure and function of the cell wall in plant cells?

Answer 14

The cell wall is made of cellulose and provides structural support and protection to plant cells.

Question 15

What is the function of chloroplasts in plant cells?

Answer 15

Chloroplasts contain chlorophyll, which absorbs light energy for photosynthesis to produce glucose.

Question 16

What are specialized cells and how are they adapted to their functions?
Give an example

Answer 16

Specialized cells are adapted to perform specific functions more efficiently. such as red blood cells for oxygen transport (with no nucleus and hemoglobin)

Question 17

What is the difference between plant and animal cells?

Answer 17

Plant cells have 3 extras that animal cells don’t have such as a chloroplast, cell wall, vacuole.

Question 18

Describe the stages of mitosis.

Answer 18

1) DNA replicates to form two copies of each chromosome
The cells grows and increases in sub cellular structures such as ribosome and mitochondria
2) one set of chromosomes is pulled to opposite side of the cell and the nucleus divides
3) the cytoplasm and cell membrane divide (cytokinesis) to form genetically identical cells

Question 19

What is the function of the vacuole in plant cells?

Answer 19

The vacuole stores cell sap, which helps maintain turgidity and stores water, nutrients, and waste products.

Question 20

What is the role of stem cells?

Answer 20

Stem cells can differentiate into various types of cells and are important for growth, development, and repair.

Question 21

Name a specialised cell for reproduction

Answer 21

Sperm Cell
To deliver the male DNA to the female egg.

Specialisations:
•Long tail and streamlined head help it swim efficiently to the egg.
•Packed with mitochondria to release energy through respiration for movement.

Question 22

Name a specialised cell for rapid signalling

Answer 22

Nerve cells
Carry electrical impulses (signals) across long distances in the body.
Long length allows them to transmit signals quickly over large distances.
Branch ends (dendrites) connect with other nerve cells to form communication networks.

Question 23

Name a specialised cell for contraction

Answer 23

Muscle cells
To contract (shorten) quickly and generate force for movement.

Long cells provide space for contraction proteins.
Contain lots of mitochondria to release energy for contraction.
Contain protein fibres (actin and myosin) that slide past each other to shorten the cell.

Question 24

Name a specialised cell for absorbing water and minerals

Answer 24

Root hair cell

Absorb water and mineral ions from the soil.
Long extensions (root hairs) increase surface area for absorption.
Thin cell wall allows water to pass through easily by osmosis.
Large vacuole maintains a concentration gradient for water uptake.

Question 25

Name a specialised cell for transporting substances

Answer 25

Phloem and xylem Transport water, minerals (xylem), and food/sugars (phloem). Xylem cells: Hollow and dead — no internal structures, allowing easy water flow. Strengthened by lignin for structural support. Phloem cells: Few subcellular structures so substances can flow. Companion cells help with energy for active transport.

Question 26

What is binary fission?

Answer 26

A type of asexual reproduction in prokaryotic cells where the cell splits into two.

Question 27

What happens during binary fission?

Answer 27

1. Circular DNA and plasmids replicate. 2. Cell grows and DNA strands move to opposite ends. 3. Cytoplasm begins to divide. 4. Two identical daughter cells are formed.

Question 28

How quickly can bacteria divide by binary fission?

Answer 28

Every 20 minutes if conditions are ideal

Question 29

What features make exchange surfaces efficient?

Answer 29

Large surface area, thin membrane (short diffusion path), good blood supply, and ventilation (in gas exchange).

Question 30

How are alveoli adapted for gas exchange?

Answer 30

Large surface area, moist lining, thin walls, and a good blood supply.

Question 31

How are villi in the small intestine adapted for absorption

Answer 31

Large surface area, thin walls, and a rich blood supply for efficient diffusion of nutrients.

Question 32

How are leaves adapted for gas exchange

Answer 32

Large surface area, stomata for gas exchange, and thin for short diffusion path.

Question 33

What is differentiation

Answer 33

The process where a cell changes to become specialised at its job

Question 34

How are stem cells used in medicine?

Answer 34

Stem cells can be used to replace damaged cells, Nerve cells for people with paralysis Insulin-producing cells for people with diabetes Therapeutic cloning creates a stem cell with same genetic material as the patient

Question 35

What are the risks and ethical issues of using stem cells?

Answer 35

Unethical using embryos destroys potential life religious reasons risk of uncontrollable cell division cancer may become contaminated with other viruses Allowed in uk with strict rules

Question 36

Where are stem cells found in plants and how are they used?

Answer 36

Found in meristems they can differentiate into anything throughout its life Used to clone rare species and produce disease-resistant crops.

Question 37

What are the three main ways substances move across cell membranes?

Answer 37

• Diffusion – movement of particles from high to low concentration. • Osmosis – diffusion of water from a dilute to a concentrated solution through a partially permeable membrane. • Active transport – movement against the concentration gradient using energy from respiration.

Question 38

How are exchange surfaces to adapt for effective diffusion

Answer 38

• Large surface area • Thin membrane (short diffusion distance) • Good blood supply (in animals) • Ventilation (in gas exchange systems like lungs)

Question 39

How are the lungs adapted for gas exchange?

Answer 39

• Alveoli provide a large surface area. • Moist walls and thin walls (1 cell thick) for efficient diffusion. • Rich blood supply maintains a concentration gradient. • Ventilation ensures a constant supply of oxygen and removal of carbon dioxide.

Question 40

How do roots and leaves in plants exchange substances

Answer 40

• Root hair cells absorb water (by osmosis) and minerals (by active transport). • Leaves: • Stomata allow gases (CO₂ in, O₂ out) to diffuse. • Guard cells control gas exchange by opening and closing stomata. • Flat, thin shape and air spaces in the leaf aid diffusion.

Question 41

How are fish gills adapted for efficient gas exchange?

Answer 41

Gills are specialised gas exchange surfaces in fish that extract oxygen from water. • Key adaptations: • Gill filaments provide a large surface area. • Lamellae on filaments further increase surface area and contain capillaries for good blood supply. • Thin surface layer of cells for a short diffusion distance. • Counter-current flow system: • Blood flows through the lamellae in the opposite direction to the water. • This maintains a steep concentration gradient across the entire gill, so maximum oxygen diffusion occurs.